Synergistic mixtures of nickel-containing 2,2&#39;-thiobis(alkylphenols) and 2-hydroxy-4-alkoxybenzophenones

ABSTRACT

Stabilizer systems containing at least two Ni-containing light-stabilizers in which nickel (which, in class 2, optionally contains an additional ligand) forms a complex compound with a compound selected from the group consisting of the classes: 
     1. 2-hydroxy-4-alkoxybenzophenones 
     2. 2,2&#39;-thiobis[4-alkylphenols] 
     3. 3,5-dialkyl-4-hydroxybenzoic acid monoalkyl esters 
     4. 3,5-dialkyl-4-hydroxybenzylphosphonic acid monoalkyl esters 
     5. 1-phenyl-3-methyl-4-acyl-5-hydroxypyrazole, 
     in which the radicals generally contained are appropriately substituted. After being incorporated into the corresponding polyolefins, these stabilizer systems have a synergistic effect which prevents or at least greatly retards decomposition initiated by light and/or oxygen.

This is a divisional of application Ser. No. 688,090, filed on Dec. 31,1984, now U.S. Pat. No. 4,623,480, issued on Nov. 18, 1986.

The present invention relates to mixtures of nickel stabilisers andtheir use for the improved stabilisation of polyolefins against theaction of light.

Like other substances, organic plastics materials undergo certainchanges in their properties in the course of time, these changesoccurring more or less rapidly depending on the influences by which theyare caused. The changes can generally be more or less prevented by theaddition of so-called stabilisers to the polymer. It is known thatadditives can be added to organic polymers in order to protect thesesubstrates from decomposition initiated by light or atmospheric oxygen.Great demands are made on additives; they should therefore be able toprevent or at least greatly retard the ageing phenomena of an organicpolymer. For example, yellowing phenomena, loss of surface lustre ortransparency, and also loss of impact strength, flexural strength andstretching ability should be largely suppressed. It is known, forexample, from DE-AS No. 1 144 004 that polyolefins can be protectedagainst decomposition caused by light and heat using Ni-phenolates ofbi-(alkylphenol)-monosulphides. In addition, it is known from SwissPatent Specification No. 457 837 that nickel salts of certain phosphonicacids or phosphonic acid semi-esters prevent the discoloration ofpolymeric organic substances under the influence of light. Thosestabilisers are not, however, equal to the increased demands in everyrespect.

It has now been found that compositions based on polyolefins andcontaining at least two nickel stabilisers known per se as agents forstabilising plastics against the action of light (referred to herein as"light-stabilisers") have a surprising synergistic effect as regards theprotection of the polyolefin against decomposition caused by lightsince, although the Ni-containing stabilisers used in these compositionsare themselves light-stabilisers, they do not have the degree ofactivity now obtained.

The present invention relates to compositions containing at least twoNi-containing light-stabilisers selected from the group that consists ofthe classes:

1. compounds having the formula I ##STR1## in which R represents C₁ -C₁₂alkyl, 2. compounds having the formula II or II' ##STR2## in which R'represents C₁ -C₈ alkyl and in which nickel in the formula II' mayoptionally contain an additional ligand A, such as primary or secondaryC₁ -C₁₈ alkylamine, triethanolamine, cyclohexyldiethanolamine oraniline, anisidine, toluidine, 1-naphthylamine, 2-naphthylamine,p-butylaniline, xylidine, p-octyloxyaniline or morpholine,hexamethyleneimine, piperazine or piperidine,

3. compounds having the formula III ##STR3## in which R¹ and R² are thesame or different and represent C₁ -C₄ alkyl,

4. compounds having the formula IV ##STR4## in which R³ and R⁴ are thesame or different and represent C₁ -C₄ alkyl and R⁵ represents C₁ -C₁₈alkyl, and

5. compounds having the formula V ##STR5## in which R⁶ represents C₄-C₁₂ alkyl.

In formula I, R may be straight-chained or branched; preferably, R isstraight-chained and represents C₄ -C₁₂ alkyl, C₄ -C₁₂ alkyl beingn-butyl, n-hexyl, n-octyl, n-nonyl, n-decyl or n-dodecyl, preferablyn-octyl, n-decyl or n-dodecyl.

In formulae II and II', R' may be straight-chained or branched;preferably, R' is branched and represents C₄ -C₈ alkyl, C₄ -C₈ alkylbeing sec.-butyl, tert.-butyl, neopentyl, 2-diethylbutyl or tert.-octyl,preferably tert.-octyl. Tert.-octyl should be taken as meaning1,1,3,3-tetramethylbutyl.

If nickel contains primary or secondary C₁ -C₁₈ alkylamine as additionalligand A (in formula II'), the amine-substituents are straight-chain orbranched alkyl radicals, preferably straight-chain C₁ -C₁₂ alkylradicals, especially n-propyl, n-butyl or n-dodecyl.

In formula III, R¹ and R² may be straight-chained or branched; they arepreferably identical and branched and represent, especially,tert.-butyl.

In formula IV, R³ and R⁴ may be straight-chained or branched; they arepreferably identical and branched and in that case represent,especially, tert.-butyl. The substituent R⁵ may also be straight-chainedor branched and represents, for example, methyl, ethyl, n-propyl,isopropyl, n-butyl, sec.-butyl, tert.-butyl, n-pentyl or n-hexyl, butpreferably methyl, ethyl, n-propyl or n-butyl.

In formula V, R⁶ may be straight-chained or branched and preferablyrepresents C₈ -C₁₂ alkyl, it being possible for the following radicalsto be present: n-octyl, n-nonyl, n-decyl, n-undecyl or n-dodecyl,especially n-nonyl.

There may optionally be a further ligand, such as the ligand A given inclass 2, in the nickel compounds of classes 1, 3, 4 and 5.

Preferred are those compositions containing two Ni-containinglight-stabilisers in which one Ni-containing compound is based on class2 and the other may originate from any one of classes 1, 3, 4 and 5.

Also preferred are compositions containing two Ni-containinglight-stabilisers in which one Ni-containing compound is based on class3 and the other may originate from either of classes 1 and 5.

Finally, there are preferred compositions containing two Ni-containinglight-stabilisers in which one Ni-containing compound originates fromclass 1 and the other originates from class 5.

Especially preferred are compositions containing two Ni-containinglight-stabilisers that are selected from the group consisting of

(a) 2,2'-thiobis(4-tert.-octylphenolato)-butylaminonickel(II)/nickel(II)chelate of 2-hydroxy-4-octyloxybenzophenone

(b) 2,2'-thiobis(4-tert.-octylphenolato)-butylaminonickel(II)/nickel-bis(1-phenyl-3-methyl-4-decanoyl-5-pyrazolate)

(c)2,2'-thiobis[4-tert.-octylphenolato]-butylaminonickel(II)/nickel-bis[(ethyl-(3,5-di-tert.-butyl-4-hydroxybenzyl)-phosphonate)]

(d)2,2'-thiobis[4-tert.-octylphenolato]-butylaminonickel(II)/bis[2,2'-thiobis(4-tert.-octylphenolato)]-nickel(II)

(e) nickel(II) chelate of2-hydroxy-4-octyloxybenzophenone/bis[2,2'-thiobis(4-tert.-octylphenolato)]-nickel(II)

(f) nickel(II) chelate of2-hydroxy-4-octyloxybenzophenone/nickel-bis(1-phenyl-3-methyl-4-decanoyl-5-pyrazolate)

(g)nickel-bis[(ethyl-(3,5-di-tert.-butyl-4-hydroxybenzyl)-phosphonate]/bis[2,2'-thiobis(4-tert.-octylphenolato)]-nickel(II)and

(h)bis[2,2'-thiobis(4-tert.-octylphenolato)]-nickel(II)/nickel-bis(1-phenyl-3-methyl-4-decanoyl-5-pyrazolate).

Especially preferred are compositions containing two Ni-containinglight-stabilisers that are selected from the group consisting of

(A)2,2'-thiobis(4-tert.-octylphenolato)-butylaminonickel(II)/nickel-bis[(ethyl-(3,5-di-tert.-butyl-4-hydroxybenzyl)-phosphonate)]

(B)2,2'-thiobis(4-tert.-octylphenolato)-butylaminonickel(II)/nickel-bis(1-phenyl-3-methyl-4-decanoyl-5-pyrazolate)

(C) 2,2'-thiobis(4-tert.-octylphenolato)-butylaminonickel(II)/nickel(II)chelate of 2-hydroxy-4-octyloxybenzophenone

(D)bis[2,2'-thiobis(4-tert.-octylphenolato)]-nickel(II)/nickel-bis(1-phenyl-3-methyl-4-decanoyl-5-pyrazolate)and

(E) bis[2,2'-thiobis(4-tert.-octylphenolato)]-nickel(II)/nickel(II)chelate of 2-hydroxy-4-octyloxybenzophenone.

The Ni-compounds occurring in the stabiliser systems according to theinvention are manufactured according to known methods, such asdescribed, for example, in Patent Specifications GB Nos. 943,081,991,591, U.S. Pat. Nos. 3,029,276, 3,189,630, 3,310,575, CH No. 457,837and U.S. Pat. No. 4,008,200. A number of the compounds are alsocommercially available.

Examples of plastics materials that can be provided with the stabilisermixture according to the invention are:

1. Polymers of mono- and di-olefins, for example polyethylene (which mayoptionally be cross-linked), polypropylene, polyisobutylene,polybut-1-ene, polymethylpent-1-ene, polyisoprene or polybutadiene andalso polymers of cyclo-olefins, such as, for example, cyclopentene ornorbornene.

2. Mixtures of the polymers mentioned under 1., for example mixtures ofpolypropylene with polyisobutylene.

3. Copolymers of mono- and di-olefins with one another or with othervinyl monomers, such as, for example, ethylene/propylene copolymers,propylene/but-1-ene copolymers, propylene/isobutylene copolymers,ethylene/but-1-ene copolymers, ethylene/pent-1-ene copolymers,ethylene/4-methyl-1-pentene copolymers, ethylene/hex-1-ene copolymers,ethylene/oct-1-ene copolymers, propylene/butadiene copolymers,isobutylene/isoprene copolymers, ethylene/alkyl acrylate copolymers,ethylene/alkyl methacrylate copolymers, ethylene/vinyl acetatecopolymers or ethylene/acrylic acid copolymers and salts thereof(ionomers), and also terpolymers of ethylene with propylene and a diene,such as hexadiene, dicyclopentadiene or ethylidenenorbornene.

4. Mixtures (polyblends) of the above-mentioned polymers, such as, forexample, PP/EPDM.

Of great importance are, especially, polyolefins, and, very especially,polypropylene and polyethylene.

The compositions according to the invention are added to the polyolefinsin a concentration of from 0.005 to 5% by weight, based on the weight ofthe polyolefin to be stabilised. Preferably, from 0.05 to 2% by weightand especially from 0.1 to 2% by weight of the compositions, based onthe material to be stabilised, are incorporated into that material.

If the compositions according to the invention constitute a stabilisersystem consisting of two stabilisers, then these are added to thepolyolefin in a ratio of from 1:20 to 20:1.

The incorporation can be carried out, for example, by mixing in theNi-containing light-stabilisers according to the invention, andoptionally other additives, according to methods customary in the art,before or during shaping, or alternatively by applying the dissolved ordispersed compounds to the polymer, optionally with subsequentevaporation of the solvent. The additives can be incorporated separatelyor in the form of a mixture.

The compositions according to the invention can also be added to theplastics materials to be stabilised in the form of a master batch thatcontains these compounds, for example, in a concentration of from 2.5 to25% by weight.

In the case of cross-linked polyethylene, the compositions according tothe invention are added before cross-linking takes place.

The materials stabilised in this manner can be used in a wide variety offorms, for example in the form of films, especially agrofilms, fibres,tapes, moulding compositions, profiles, foamed articles or in the formof binders for lacquers, adhesives or cements.

In practice, the compositions according to the invention can be usedtogether with other stabilisers. Examples of other additives togetherwith which the stabilisers employed according to the invention can beused, are:

1. Antioxidants 1.1. Alkylated monophenols

2,6-di-tert.-butyl-4-methylphenol

2-tert.-butyl-4,6-dimethylphenol

2,6-di-tert.-butyl-4-ethylphenol

2,6-di-tert.-butyl-4-n-butylphenol

2,6-di-tert.-butyl-4-isobutylphenol

2,6-di-cyclopentyl-4-methylphenol

2-(α-methylcyclohexyl)-4,6-dimethylphenol

2,6-di-octadecyl-4-methylphenol

2,4,6-tri-cyclohexylphenol

2,6-di-tert.-butyl-4-methoxymethylphenol

1.2. Alkylated hydroquinones

2,6-di-tert.-butyl-4-methoxyphenol

2,5-di-tert.-butylhydroquinone

2,5-di-tert.-amylhydroquinone

2,6-diphenyl-4-octadecyloxyphenol

1.3. Hydroxylated thiodiphenyl ethers

2,2'-thiobis(6-tert.-butyl-4-methylphenol)

2,2'-thiobis(4-octylphenol)

4,4'-thiobis(6-tert.-butyl-3-methylphenol)

4,4'-thiobis(6-tert.-butyl-2-methylphenol)

1.4. Alkylidene bisphenols

2,2'-methylene-bis(6-tert.-butyl-4-methylphenol)

2,2'-methylene-bis(6-tert.-butyl-4-ethylphenol)

2,2'-methylene-bis[4-methyl-6-(α-methylcyclohexyl)-phenol]

2,2'-methylene-bis(4-methyl-6-cyclohexylphenol)

2,2'-methylene-bis(6-nonyl-4-methylphenol)

2,2'-methylene-bis(4,6-di-tert.-butylphenol)

2,2'-ethylidene-bis(4,6-di-tert.-butylphenol)

2,2'-ethylidene-bis(6-tert.-butyl-4-isobutylphenol)

2,2'-methylene-bis[6-(α-methylbenzyl)-4-nonylphenol]

2,2'-methylene-bis[6-(α,α-dimethylbenzyl)-4-nonylphenol]

4,4'-methylene-bis(2,6-di-tert.-butylphenol)

4,4'-methylene-bis(6-tert.-butyl-2-methylphenol)

1,1-bis(5-tert.-butyl-4-hydroxy-2-methylphenyl)-butane

2,6-di-(3-tert.-butyl-5-methyl-2-hydroxybenzyl)-4-methylphenol

1,1,3-tris(5-tert.-butyl-4-hydroxy-2-methylphenyl)butane

1,1-bis(5-tert.-butyl-4-hydroxy-2-methylphenyl)-3-n-dodecylmercaptobutane

ethylene glycol-bis[3,3-bis-(3'-tert.-butyl-4'-hydroxyphenyl)-butyrate]

di-(3-tert.-butyl-4-hydroxy-5-methylphenyl)-dicyclopentadiene

di-[2-(3'-tert.-butyl-2'-hydroxy-5'-methylbenzyl)-6-tert.-butyl-4-methylphenyl]-terephthalate

1.5. Benzyl compounds

1,3,5-tri-(3,5-di-tert.-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene

di-(3,5-di-tert.-butyl-4-hydroxybenzyl)-sulphide

3,5-di-tert.-butyl-4-hydroxybenzylmercaptoacetic acid isooctyl ester

bis(4-tert.-butyl-3-hydroxy-2,6-dimethylbenzyl)-dithiol-terephthalate

1,3,5-tris(3,5-di-tert.-butyl-4-hydroxybenzyl)-isocyanurate

1,3,5-tris(4-tert.-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate

3,5-di-tert.-butyl-4-hydroxybenzylphosphonic acid dioctadecyl ester

calcium salt of 3,5-di-tert.-butyl-4-hydroxybenzylphosphonic acidmonoethyl ester

1.6. Acylaminophenols

4-hydroxylauric acid anilide

4-hydroxystearic acid anilide

2,4-bisoctylmercapto-6-(3,5-di-tert.-butyl-4hydroxy-anilino)-s-triazine

N-(3,5-di-tert.-butyl-4-hydroxyphenyl)-carbamic acid octyl ester

1.7. Esters of β-(3,5-di-tert.-butyl-4-hydroxyphenyl)-propionic acidwith monohydric or polyhydric alcohols, such as, for example, with

methanol; diethylene glycol; octadecanol; triethylene glycol;1,6-hexanediol; pentaerythritol; neopentyl glycol; trishydroxyethylisocyanurate; thiodiethylene glycol; di-hydroxyethyloxalic acid diamide.

1.8. Esters of β-(5-tert.-butyl-4-hydroxy-3-methylphenyl)-propionic acidwith monohydric or polyhydric alcohols, such as, for example, with

methanol; diethylene glycol; octadecanol; triethylene glycol;1,6-hexanediol; pentaerythritol; neopentyl glycol; trishydroxyethylisocyanurate; thiodiethylene glycol; di-hydroxyethyloxalic acid diamide.

1.9. Amides of β-(3,5-di-tert.-butyl-4-hydroxyohenyl)-propionic acid,such as, for example,

N,N'-di-(3,5-di-tert.-butyl-4-hydroxyphenylpropionyl)hexamethylenediamine

N,N'-di-(3,5-di-tert.-butyl-4-hydroxyphenylpropionyl)trimethylenediamine

N,N'-di-(3,5-di-tert.-butyl-4-hydroxyphenylpropionyl)hydrazine

2. UV-Absorbers and light-stabilisers 2.1.2-(2'-Hydroxyphenyl)-benzotriazoles, such as, for example,

the 5'-methyl, 3',5'-di.-tert.-butyl, 5'-tert.-butyl,5'-(1,1,3,3-tetramethylbutyl), 5'-chloro-3',5'-di-tert.-butyl,5-chloro-3'-tert.-butyl-5'-methyl, 3'-sec.-butyl-5'-tert.-butyl,4'-octyloxy, 3',5'-di-tert.-amyl or 3',5'-bis(α,α-dimethylbenzyl)derivative

2.2. 2-Hydroxybenzophenones, such as, for example,

the 4-hydroxy, 4-methoxy, 4-octyloxy, 4-decyloxy, 4-dodecyloxy,4-benzyloxy, 4,2',4'-trihydroxy or 2'-hydroxy-4,4'-dimethoxy derivative.

2.3. Esters of optionally substituted benzoic acids, such as, forexample,

4-tert.-butylphenyl salicylate, phenyl salicylate, octylphenylsalicylate, dibenzoyl-resorcinol, bis(4-tert.-butylbenzoyl)-resorcinol,benzoylresorcinol, 3,5-di-tert.-butyl-4-hydroxybenzoic acid2,4-di-tert.-butylphenyl ester or 3,5-di-tert.-butyl-4-hydroxybenzoicacid hexadecyl ester.

2.4. Acrylates, such as, for example,

α-cyano-β,β-diphenylacrylic acid ethyl ester or isooctyl ester,α-methoxycarbonylcinnamic acid methyl ester,α-cyano-β-methyl-p-methoxycinnamic acid methyl ester or butyl ester,α-methoxycarbonyl-p-methoxycinnamic acid methyl ester orN-(β-methoxycarbonyl-β-cyanovinyl)-2-methylindoline.

2.5. Nickel compounds, such as, for example,

nickel complexes of 2,2'-thiobis[4-(1,1,3,3-tetramethylbutyl)-phenol],such as the 1:1- or the 1:2-complex, with additional ligands, such astriethanolamine or N-cyclohexyldiethanolamine, nickel dibutyldithiocarbamate, nickel complexes of ketoximes, such as of2-hydroxy-4-methylphenyl undecyl ketone oxime or nickel complexes of1-phenyl-4-lauroyl-5-hydroxypyrazole, optionally with additionalligands.

2.6. Sterically hindered amines, such as, for example,

bis(2,2,6,6-tetramethylpiperidyl)-sebacatebis(1,2,2,6,6-pentamethylpiperidyl)-sebacaten-butyl-3,5-di-tert.-butyl-4-hydroxybenzylmalonic acidbis(1,2,2,6,6-pentamethylpiperidyl)-ester, condensation product of1-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinicacid, condensation product ofN,N'-(2,2,6,6-tetramethylpiperidyl)-hexamethylenediamine and4-tert.-octylamino-2,6-dichloro-1,3,5-s-triazine,tris(2,2,6,6-tetramethylpiperidyl)-nitrilotriacetate,tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylicacid, 1,1'-(1,2-ethanediyl)-bis(3,3,5,5-tetramethylpiperazinone).

2.7. Oxalic acid diamides, such as, for example,

4,4'-di-octyloxyoxanilide,2,2'-di-octyloxy-5,5'-di-tert.-butyloxanilide,2,2'-di-dodecyloxy-5,5'-di-tert.-butyloxanilide,2-ethoxy-2'-ethyloxanilide, N,N'-bis(3-dimethylaminopropyl)-oxalamide,2-ethoxy-5-tert.butyl-2'-ethyloxanilide and its mixture with2-ethoxy-2'-ethyl-5,4'-di-tert.-butyloxanilide or mixtures of ortho- andpara-methoxy- and of o- and p-ethoxy-di-substituted oxanilides.

3. Metal deactivators, such as, for example,

N,N'-diphenyloxalic acid diamide, N-salicylal-N'-salicyloylhydrazine,N,N'-bissalicyloylhydrazine,N,N'-bis(3,5-di-tert.-butyl-4-hydroxyphenylpropionyl)-hydrazine,3-salicyloylamino-1,2,4-triazole or bisbenzylideneoxalic aciddihydrazide.

4. Phosphites and phosphonites, such as, for example,

triphenyl phosphite, diphenylalkyl phosphites, phenyldialkyl phosphites,tri-(nonylphenyl)-phosphite, trilauryl phosphite, trioctadecylphosphite, distearylpentaerythritol diphosphite,tris(2,4-di-tert.-butyl-phenyl)-phosphite, diisodecylpentaerythritoldi-phosphite, di-(2,4-di-tert.-butylphenyl)-pentaerythritol diphosphite,tristearylsorbitol triphosphite ortetrakis(2,4-di-tert.-butylphenyl)-4,4'-biphenylene diphosphonite.

5. Peroxide-destroying compounds, such as, for example,

esters of β-thiodipropionic acid, for example the lauryl, stearyl,myristyl or tridecyl ester, mercaptobenzimidazole, the zinc salt of2-mercaptobenzimidazole, zinc dibutyl dithiocarbamate, di-octadecyldisulphide or pentaerythritol tetrakis(β-dodecylmercapto)-propionate.

6. Basic co-stabilisers, such as, for example,

melamine, polyvinylpyrrolidone, dicyanodiamide, triallyl cyanurate, ureaderivatives, hydrazine derivatives, amines, polyamides, polyurethanes,alkali and alkaline earth salts of higher fatty acids, for example Castearate, Zn stearate, Mg stearate, Na ricinoleate, K palmitate,antimony pyrocatecholate or tin pyrocatecholate.

7. Nucleation agents, such as, for example,

4-tert.-butylbenzoic acid, adipic acid or diphenylacetic acid.

8. Fillers and reinforcing agents, such as, for example,

calcium carbonate, silicates, glass fibres, asbestos, talc, kaolin,mica, barium sulphate, metal oxides and hydroxides, carbon black orgraphite.

9. Other additives, such as, for example,

plasticisers, glidants, emulsifiers, pigments, optical brighteners,flame-proofing agents, antistatic agents or propellants.

The synergistic mixtures are explained in more detail by means of thefollowing Example.

EXAMPLE 1 (a) Preparation of the samples

100 parts of low-density polyethylene powder (d=0.917) are mixedhomogeneously in a Brabender plastograph for ten minutes at atemperature of 180oC with 0.15% by weight of the stabilisers listed inTable 1 or with 0.075% by weight of the first stabiliser component andwith 0.075% by weight of the second stabiliser component (listed inTable 2). The homogenised mass is then pressed in a laboratory press toform a plate from 2 to 3 mm thick. Parts of this plate are, again in apress, exposed to a temperature of 170° C. and a pressure of 12 torr; afilm 0.1 mm thick is formed which is quenched with cold water. Samplesmeasuring 60×40 mm are cut out of this film.

(b) Test method

The film samples are irradiated in a XENOTEST 1200 apparatus. Thesamples are analysed at regular intervals in an IR spectrophotometer,the extinction at 5.85 μm being measured as an indication of thecarbonyl content of the sample under examination. An increase in thecarbonyl extinction is a measure of the photooxidative decomposition ofthe polymer (see Balaban et al., J. Pol. Sci., Part C, 22 (1969),1059-1071) and is connected with the material's loss of mechanicalstrength. Irradiation is continued until a carbonyl extinction of 0.100is achieved. The irradiation times T₀.1 up to this degree of damage aregiven in the following two Tables.

First, however, the following abbreviations should be introduced inorder to simplify the designation of the stabilisers alone and in thesynergistic mixtures, numbers being assigned to the individualcompounds: ##STR6##

                  TABLE 1                                                         ______________________________________                                        XENOTEST 1200 up to 0.1 carbonyl extinction for                               Ni--complexes in "low-density" polyethylene                                                 Additive content                                                                           T.sub.0.1                                          Additive No.  [% by weight]                                                                              [h]                                                ______________________________________                                        1             0.15         510                                                2             0.15         1330                                               3             0.15         630                                                4             0.15         860                                                5             0.15         1000                                               6             0.15         1300                                               control       none         250                                                ______________________________________                                    

                                      TABLE 2                                     __________________________________________________________________________    XENOTEST 1200 up to 0.1 carbonyl extinction for synergistic                   Ni-- stabiliser mixtures in                                                   "low-density" polyethylene.                                                   (A and B represent the numbers assigned to the nickel stabilisers; % by       weight is abbreviated to %).                                                  Stabiliser mixture      (T.sub.0.1).sub.0.15% A + (T.sub.0.1).sub.0.15%                               B                                                     0.075% A + 0.075% B                                                                       (T.sub.0.1).sub.0.075% A+ 0.075% B                                                        2             (T.sub.0.1).sub.0.15%                                                                (T.sub.0.1).sub.0.15% B          A/B         [h]         [h]           [h]    [h]                              __________________________________________________________________________    5/2         1450        1165          1000   1330                             5/4         1510        930           1000   860                              2/3         1820        980           1330   630                              2/1         1670        920           1330   510                              4/3         1120        745            860   630                              5/3          940        815           1000   630                              2/4         1140        1095          1330   860                              4/1          890        685            860   510                              __________________________________________________________________________

It can be seen from these results that the stabiliser mixtures given inTable 2 have a synergistic effect.

I claim:
 1. A stabilizer composition containing at least oneNi-containing light stabilizer selected from each of class I and ofclass II or from each of class I and of class II':class I compoundshaving the formula I ##STR7## in which R represents C₁ -C₁₂ -alkyl, andclass II or class II' compounds having the formula II or II' ##STR8## inwhich R' represents C₁ -C₈ -alkyl and in which nickel in formula II'optionally contains an additional ligand A which is a primary orsecondary C₁ -C₁₈ -alkylamine, triethanolamine,cyclohexyldiethanolamine, aniline, anisidine, toluidine,1-naphthylamine, 2-naphthylamine, p-butylaniline, xylidine,p-octyloxyaniline, morpholine, hexamethyleneimine, piperazine orpiperidine.
 2. A stabilizer composition according to claim 1 containingtwo nickel-containing light stabilizers selected from the groupconsisting of(a) 2,2'-thiobis(4-tert-octylphenolato)-butylaminonickel(II)/nickel(II) chelate of 2-hydroxy-4-octyloxybenzophenone, and(e) nickel(II) chelate of2-hydroxy-4-octyloxybenzophenone/bis[2,2'-thiobis(4-tert-octylphenolato)]-nickel(II).